Optical component

ABSTRACT

A touch sensing apparatus is provided comprising: a light transmissive panel that defines a touch surface, a plurality of light emitters and detectors arranged along a perimeter of the light transmissive panel, a plurality of optical components arranged along the perimeter of the light transmissive panel, wherein the light emitters are arranged to emit a respective beam of emitted light and the optical components are configured to direct the emitted light to a path across the light transmissive panel. Optionally, optical components comprise a light guide arranged to receive light from the light emitters through a first surface and couple out light travelling in the light guide to the touch surface through a second surface. The second surface may be diffusively transmissive. The light guide may further comprise a reflective surface configured to internally reflect light travelling in the light guide from the first surface to the diffusive surface. The reflective surface may be diffusely reflective, partially diffusely reflective, or specularly reflective.

TECHNICAL FIELD

The present invention relates to touch-sensing apparatus that operate by propagating light by diffusive light scattering above a panel, and in particular to optical and mechanical solutions for defining the light paths over the panel. The present invention relates furthermore to a method of assembling a touch sensing apparatus.

BACKGROUND ART

In one category of touch-sensitive panels known as ‘above surface optical touch systems’, a set of optical emitters are arranged around the periphery of a touch surface to emit light that is reflected to travel above the touch surface. A set of light detectors are also arranged around the periphery of the touch surface to receive light from the set of emitters from above the touch surface. An object that touches the touch surface will attenuate the light on one or more propagation paths of the light and cause a change in the light received by one or more of the detectors. The location (coordinates), shape or area of the object may be determined by analysing the received light at the detectors.

Some prior art systems rely on coupling and propagation of collimated light across the light transmissive panel. Such systems are cumbersome to reliably implement due to the small tolerances with respect to the alignment of the components thereof. E.g. the light emitters- and detectors need to be precisely aligned in relation to various lenses and reflect the light via concave and/or convex reflection and/or refraction to get the desired collimation. Such precise alignment may be difficult to achieve in mass production. The use of collimated light also adds to this complexity, which in turn results in a more expensive and less compact system. Furthermore, to reduce system cost, it may be desirable to minimize the number of electro-optical components.

BRIEF DESCRIPTION OF DRAWINGS

These and other aspects, features and advantages of which examples of the invention are capable of will be apparent and elucidated from the following description of examples of the present invention, reference being made to the accompanying drawings, in which;

FIGS. 1a, 1b, 1c shows an embodiment with a diffusive transmissive light guide configured to direct and receive light around the edge of the panel.

FIG. 2 shows an embodiment with a diffusive transmissive light guide configured to direct and receive light around the edge of the panel.

FIGS. 3a, 3b show an embodiment with a diffusive reflective component configured to direct and receive light around the edge of the panel.

FIGS. 4a, 4b shows another embodiment with a diffusive reflective light guide configured to direct and receive light around the edge of the panel.

FIG. 5 shows another embodiment with a diffusive reflective light guide configured to direct and receive light around the edge of the panel.

FIG. 6 shows an embodiment with a diffusive reflective component configured to direct and receive light through the panel.

FIGS. 7a, 7b show another embodiment with a diffusive reflective light guide configured to direct and receive light through the panel.

FIG. 8 shows an embodiment with a specular reflective component configured to direct and receive light through the panel.

FIG. 9 shows another embodiment with a specular reflective light guide configured to direct and receive light through the panel.

FIG. 10 shows another embodiment with multiple specular reflective light guides configured to direct and receive light around the edge of the panel.

FIG. 11 shows an embodiment with a reflective component comprising an angular filter.

FIG. 12a shows an embodiment with a reflective component and an elongate channel having light absorbing walls.

FIG. 12b shows an embodiment with a diffusive surface and a second reflective surface.

FIGS. 13a, 13b show an embodiment with a reflective light guide incorporating an elongate channel having light absorbing walls.

FIG. 14 shows another embodiment with a reflective light guide incorporating an elongate channel having light absorbing walls.

FIG. 15 shows another embodiment with a reflective light guide incorporating an elongate channel having light absorbing walls.

FIG. 16 shows an embodiment with a reflective light guide incorporating a support member.

FIG. 17 shows an embodiment with a reflective light guide incorporating an elongate channel having with at least two channel axes.

FIG. 18 shows an embodiment with a reflective light guide and a PCB with a mounted emitter/detector component.

FIG. 19 shows an embodiment with a reflective light guide having a surface providing a dioptric power.

FIG. 20 shows an embodiment with a reflective light guide having a plurality of surfaces providing a dioptric power.

FIG. 21 shows an embodiment with a protective stopping component.

FIG. 22 shows an embodiment with an additional light absorbing layer.

FIG. 23 shows an embodiment with a reflective light guide wherein the surface proximal the panel is slanted.

FIG. 24 shows an embodiment comprising a contamination ditch between the light guide and the panel.

FIG. 25 shows an embodiment with a reflective light guide having a top layer comprising a high refractive index than the light guide.

FIG. 26 shows an embodiment with a reflective light guide having a hard coating layer.

FIG. 27 shows another embodiment with a reflective light guide having a hard coating layer.

FIG. 28 shows an embodiment with a reflective light guide wherein the surface proximal the panel is vertically corrugated.

SUMMARY

It is an objective of the invention to at least partly overcome one or more of the above-identified limitations of the prior art.

One or more of these objectives, as well as further objectives that may appear from the description below, are at least partly achieved by means of a method for data processing, a computer readable medium, devices for data processing, and a touch-sensing apparatus according to the independent claims, embodiments thereof being defined by the dependent claims.

An aspect of the invention provides a touch sensing apparatus, comprising: a light transmissive panel that defines a touch surface, a plurality of light emitters and detectors arranged along a perimeter of the light transmissive panel, a plurality of optical components arranged along the perimeter of the light transmissive panel, wherein the light emitters are arranged to emit a respective beam of emitted light and the optical components are configured to direct the emitted light to a path across the light transmissive panel. Optionally, optical components comprise a light guide arranged to receive light from the light emitters through a first surface and couple out light travelling in the light guide to the touch surface through a second surface. The second surface may be diffusively transmissive. The light guide may further comprise a reflective surface configured to internally reflect light travelling in the light guide from the first surface to the diffusive surface. The reflective surface may be diffusely reflective, partially diffusely reflective, or specularly reflective.

The reflective surface may be coated by at least one of a high refractive index coating and a scratch resistant coating. At least one of the first and or second surfaces may comprise a dioptric power. At least one of the first and or second surfaces may comprise a corrugation. A ditch may be formed between the second surface and the panel.

At least one protective stop may be mounted to touch sensing apparatus proximal to an optical component and extending further from the touch surface along the normal to the plane of the touch surface than any optical component surface. The optical components may comprise a reflector surface to reflect light from the light emitters to the touch surface, wherein the reflector surface reflects light diffusively, partially diffusively, or specularly.

An angular filter may be arranged between the optical components and touch surface and configured to only allow light travelling within 10 degrees of the plane of touch surface to pass between the touch surface and the optical components.

An elongate channel may be positioned between each light emitter and/or detector and a surface of a corresponding optical component, wherein the elongate channel comprising channel walls, and wherein at least a portion of the channel walls are configured to absorb light. The elongate channel may be formed from a light guide, an airgap, or other light transmissive medium.

The elongate channel may optionally not be straight and/or the channel walls comprise internally reflective surfaces.

DETAILED DESCRIPTION OF EMBODIMENTS

In the following, embodiments will be presented of touch-sensitive apparatus. Throughout the description, the same reference numerals are used to identify corresponding elements.

FIG. 1a illustrates a top plan view of an example of an optical touch-sensitive apparatus. Emitters 110 are distributed around the periphery of panel 150, to project light across the panel 150. Detectors 111 are distributed around the periphery of panel 150, to receive part of the propagating light. The light from each of emitters 110 will thereby propagate to a number of different detectors 111 on a plurality of light paths D. The light paths D may conceptually be represented as “detection lines” that extend across the touch surface 140 of panel 150. Thereby, the emitters 110 and detectors 111 collectively define a grid of detection lines D (“detection grid”) on the touch surface 140, as seen in a top plan view. The spacing of intersections in the detection grid defines the spatial resolution of the touch-sensitive apparatus 100, i.e. the smallest object that can be detected on the touch surface 140.

As used herein, the emitters 110 may be any type of device capable of emitting radiation in a desired wavelength range, for example a diode laser, a VCSEL (vertical-cavity surface-emitting laser), an LED (light-emitting diode), an incandescent lamp, a halogen lamp, etc. The emitters 110 may also be formed by the end of an optical fibre. The emitters 110 may generate light in any wavelength range. The following examples presume that the light is generated in the infrared (IR), i.e. at wavelengths above about 750 nm. Analogously, the detectors 111 may be any device capable of converting light (in the same wavelength range) into an electrical signal, such as a photo-detector, a CCD device, a CMOS device, etc.

The detectors 111 collectively provide an output signal, which is received and sampled by a signal processor. The output signal contains a number of sub-signals, also denoted “projection signals”, each representing the energy of light received by one of light detectors 111 from one of light emitters 110. Depending on implementation, the signal processor may need to process the output signal for separation of the individual projection signals. The projection signals represent the received energy, intensity or power of light received by the detectors 111 on the individual detection lines D. Whenever an object touches a detection line D, the received energy on this detection line is decreased or “attenuated”.

The signal processor may be configured to process the projection signals so as to determine a property of the touching objects, such as a position (e.g. in a x,y coordinate system), a shape, or an area. This determination may involve a straight-forward triangulation based on the attenuated detection lines, e.g. as disclosed in U.S. Pat. No. 7,432,893 and WO2010/015408, or a more advanced processing method to recreate a distribution of attenuation values (for simplicity, referred to as an “attenuation pattern”) across the touch surface 140, where each attenuation value represents a local degree of light attenuation. The attenuation pattern may be further processed by the signal processor for determination of a position, shape or area of touching objects. The attenuation pattern may be generated e.g. by any available algorithm for image reconstruction based on projection signal values, including tomographic reconstruction methods such as Filtered Back Projection, FFT-based algorithms, ART (Algebraic Reconstruction Technique), SART (Simultaneous Algebraic Reconstruction Technique), etc. Alternatively, the attenuation pattern may be generated by adapting one or more basis functions and/or by statistical methods such as Bayesian inversion. Examples of such reconstruction functions designed for use in touch determination are found in WO2009/077962, WO2011/049511, WO2011/139213, WO2012/050510, and WO2013/062471, all of which are incorporated herein by reference.

In an embodiment, the apparatus 100 also includes a controller which is connected to selectively control the activation of the emitters 110 and, possibly, the readout of data from the detectors 111. Depending on implementation, the emitters 110 and/or detectors 111 may be activated in sequence or concurrently, e.g. as disclosed in U.S. Pat. No. 8,581,884. The signal processor and the controller may be configured as separate units, or they may be incorporated in a single unit. One or both of the signal processor and the controller may be at least partially implemented by software executed by a hardware CPU.

FIG. 1b illustrates an embodiment in which the light 120 emitted by emitter 110 is transmitted through light guide 130. The light exits light guide 130 through diffusive surface 135 and is distributed so that a portion of the light travels along path 90 in a plane substantially parallel with touch surface 140. FIG. 1c shows an opposite side of touch surface 140 where the same light guide 130 plays a reverse role. In FIG. 1c , light 120 is received by surface 135 of light guide 130 which then diffusively transmits the light into light guide 130. The light is then conveyed to detector 111 through light guide 130. Diffusive surface 135 may comprise a coating or other surface finish for providing an optical diffusion. Protective surfaces 125 are provided to reflect light whilst blocking ambient light. Protective surfaces 125 may comprise a white layering, e.g. paint. In one embodiment, the paint comprises titanium dioxide. This embodiment advantageously allows an uncomplicated solution for delivering light from an emitter to touch surface 140. Protective surfaces 125 for suppressing ambient light may be provided for all embodiments provided in the present description that include a light guide.

The optical arrangement shown in all of the figures may be understood to play a transmitting role when the optical arrangement conveys light from an emitter to touch surface 110 (i.e. as explicitly shown and described in FIG. 1b ) and a receiving role when the optical arrangement conveys light from touch surface 140 to a detector 111 (i.e. as explicitly shown and described in FIG. 1c ). Unless described otherwise, the optical arrangement is understood to be the same for the transmitting role and receiving role. This advantageously allows low production costs for manufacturing of an optical touch sensitive system as the same optical arrangement is used along the periphery of the system regardless of whether it is positioned over or near a detector or an emitter. The direction of light used to describe the function of the optical arrangement may depend on the functions of the individual components of the described embodiment. i.e. Where the key features of an embodiment are important in the receiving role, the direction of light used to describe the function may be according to the receiving role.

In the embodiment shown in FIG. 1b , diffusive surface 135 is positioned at an obtuse angle 142 relative to touch surface 140. This advantageously allows a convenient cleaning edge for removing dust, a reduction in Fresnel reflections, and a smooth transition from the touch surface to a bezel. Diffusive surface 135 is preferably angled at between 130° and 160° relative to touch surface 140.

In all of the embodiments described in this description, the dimensions of the components may be understood to vary. Preferably, the optical components have a height no greater than 10 mm from touch surface 140, a depth of up to than 10 mm below the panel 150, and a distance from an edge of a panel of up to 20 mm.

In an embodiment according to FIG. 2, light 120 emitted by emitter 110 is transmitted through light guide 230. The light internally reflects off surface 235, before exiting light guide 230 through diffusive surface 236. A portion of the light travels across a plane parallel with touch surface 140. Surface 235 may be angled to optimally specularly reflect light towards relative to touch surface 140. Diffusive surface 236 is preferably angled at between 45° and 160° relative to touch surface 140.

In an embodiment according to FIG. 3a , the light emitted by emitter 110 is transmitted through gap 340. Gap 340 may be an air gap or other transmissive medium with a low refractive index. The light totally reflects off diffusive, reflective surface 335 of optical component 330. A portion of the light travels along across a plane parallel with touch surface 140. This advantageously removes the need for transmitting the light through a light guide providing better transmission. Surface 335 may be angled 342 at between 20° and 50° relative to touch surface 140.

In FIG. 3b , an embodiment similar to that shown in FIG. 3a is shown further comprising dust shield 390 forming a physical barrier preventing dust from reaching diffusive, reflective surface 335 or emitter 110. Dust shield 390 comprises a transparent window through which the light 120 may pass unhindered. Preferably, dust shield 390 forms inside edge 395 and outside edge 396, from touch surface 140 to the top edge of dust shield 390. A slope on outside edge 396 allows dust shield 390 to be effectively wiped clean. Sloping edges 395 and 396 may be angled at between 100° and 80° relative to touch surface 140.

Returning to FIG. 3a , gap 340 may be filled with a dust shield forming a physical barrier preventing dust from reaching below the glass, in much the same way as for embodiment 3b. Positioning the dust shield in this position instead of on touch surface 140 allows the size of the bezel component above touch surface 140 to be smaller than the embodiment shown in FIG. 3 b.

In an embodiment according to FIG. 4a , light 120 emitted by emitter 110 is transmitted through light guide 430. The light totally internally reflects off diffusive, reflective surface 435, before exiting light guide 430 through surface 436. This advantageously allows an embodiment similar to the embodiment shown in FIG. 3b without the need for a dust shield. Surface 435 may be angled 342 at between 10° and 50° relative to touch surface 140. Surface 435 may comprise a diffuse paint layer, a diffusive tape layer, or other diffusive reflective coating or layer. Surface 436 is preferably angled at between 100° and 80° relative to touch surface 140. Light guide 430 may be formed via co-extrusion with diffusive materials applied to surface 435.

In FIG. 4b , an embodiment similar to that shown in FIG. 4a is shown wherein light guide 430 further comprises extension 437 and diffusive layer 436. In this embodiment, light guide 430 and extension 437 are formed from a single block of material and diffusive layer 436 is formed by modifying the internal structure of the block of material. In one embodiment, gas bubbles are formed in the light guide by focused high intensity laser beams. As the bubbles are optically diffusive, the resultant effect is a plane of bubbles in the light guide forming a diffusive layer. In other embodiments, extension 437 is a separate component from light guide 430 and is attached to light guide 430 during manufacturing. In these embodiments, layer 436 may be formed by etching or by microstructures on a surface of the light guide 430 and/or extension 437.

In FIG. 5, an embodiment similar to that shown in FIG. 4a is shown further comprising mounting component 531. This advantageously allows light guide 530 to be clamped to a touch apparatus using a feature that is formed as part of the same material as the light guide. Surface 535 may be angled 510 at between 20° and 50° relative to touch surface 140. At 20°, the surface 535 will collect more light from the emitter 110 whereas at 45°, surface 535 will reflect most of the specular component of light 120 towards the touch surface 140.

In an embodiment according to FIG. 6, the light 120 emitted by emitter 110 is transmitted through panel 150. The light reflects off diffusive reflective surface 635 of component 630. A portion of the light travels along across a plane parallel with touch surface 140. The feature of transmitting the light from the emitters 110 to diffusive reflective surface 635 through panel 150 has a number of advantages over the solutions presented by the prior art. In particular, manufacture of touch-sensitive apparatus 100 becomes significantly less expensive. This feature allows an arrangement where no components need to be mounted to the edges of the panel 150, allowing expensive finishing (where the panel 150 is formed from glass) to regulate the edges of the glass to be avoided. Furthermore, fastening of the components to panel 150 is simplified and optical tolerances are improved. Surface 635 may be angled 641 at between 20° and 50° relative to touch surface 140.

In an embodiment according to FIG. 7a , the light 120 emitted by emitter 110 is transmitted through panel 150. The light internally reflects off diffusive reflective surface 735 of component 730, before exiting light guide 130 through surface 740. This advantageously allows the use of a single component mounted on the touch surface without the need for a dust cover. Surface 735 may be angled 741 at between 20° and 50° relative to touch surface 140. Surface 740 is preferably angled 742 at between 100° and 80° relative to touch surface 140.

In an embodiment similar to FIG. 7a , FIG. 7b shows an embodiment where the light 120 emitted by emitter 110 is transmitted through panel 150. The light internally reflects off diffusive reflective surface 735 of light guide 730, before exiting light guide 730 through surface 740. A portion of the light also travels through panel 150 via total internal reflection.

In an embodiment according to FIG. 8, the light 120 emitted by emitter 110 is transmitted through panel 150. The light reflects off specular or partially specular reflective surface 835 of component 830. The specular reflection of light 120 advantageously allows a much brighter light signal to reach the corresponding detector 111 than in embodiments employing diffusive surfaces above. Surface 835 may comprise a mirror coating. In another embodiment, component 830 is formed from a specularly reflective material, such as a metal.

In an embodiment according to FIG. 9, the light 120 emitted by emitter 110 is transmitted through panel 150. The light internally reflects off specular or partially specular reflective surface 935 of component 930, before exiting light guide 930 through surface 940. This advantageously allows an embodiment where the reflective surface (e.g. 935) is set back from the touch surface 140. Surface 940 is preferably angled 941 at between 100° and 80° relative to touch surface 140.

In an embodiment according to FIG. 10, the light 120 emitted by emitter 110 is transmitted through light guide 1030. The light internally reflects off specular or partially specular reflective surface 1036 of light guide 1030. The light then internally reflects off specular or partially specular reflective surface 1035, before exiting light guide 1030 through surface 1040. This U-shaped configuration of light guide 1030 advantageously allows a light guide 1030 to be clamped onto an edge of the glass.

In FIG. 11, an embodiment similar to that shown in FIG. 8 is shown further comprising angular filter 1150. The light 120 from touch surface 140 is filtered by angular filter 1150 to allow only light within a narrow angular range to reach specular or partially specular reflective surface 1135. The light 120 is then reflected by surface 1135 of component 1130 before being received by detector 111 through panel 150. Angular filter 1150 advantageously ensures a much narrower angular spectrum of light to reach detector 111, allowing significant suppression of ambient light noise. This is especially relevant to the specular embodiments described herein. Angular filters 1150 may be applied to any of the embodiments shown in the present description to filter light reaching the optical component from touch surface 140. Angular filters 1150 may also be applied between the optical components and the emitters 110/detectors 111. In an embodiment, the angular filters are manufactured by producing a stack of alternating IR transmissive (e.g. PMMA sheets) and IR blocking material. The layers are laminated together. The stack may then be stretched in a guided manner and cut into optical components.

In an embodiment according to FIG. 12a , the light 120 is received by surface 1235 of optical component 1230 from touch surface 140 which then reflects the light to detector 111 via channel 1240 having a channel axis 1260. Channel 1240 may comprise an air gap or other transmissive medium. Channel 1240 may comprise one or more light absorbent walls 1250 configured to absorb light travelling at an angle sufficiently deviant from the angle of channel axis 1260. This advantageously allows angular filtering of ambient light.

In an embodiment according to FIG. 12b , the light 120 is emitted from emitter 110 onto surface 1241 and then directed up through panel 150 to surface 1236 before being directed out across touch surface 140. Surface 1241 is a diffusive, preferably matte surface, causing a component of light 120 to be scattered. Preferably, surface 1241 comprises a matte paint, matte diffuser film, or matte surface treatment. Surface 1236 is a mirror surface providing high quality, specular reflection to light 120 of above 50%. Preferably, specular reflection of light 120 is above 60%. Surface 1236 is preferably angled at 45° from the plane of touch surface 140 with a range of ±15°. In one embodiment, surface 1236 is angled a small distance from 45° to avoid unwanted optical effects resulting from light bouncing off other surfaces of the touch system. Preferably, surface 1236 is angled between 0.5° and 3° from 45°. i.e. Between 42° and 44.5° or between 45.5° and 48°. Where optical component 1230 is an anodized extruded component made from aluminium or other suitable metal, mirrored surface 1236 may be formed through diamond cut milling of component 1230 to produce the mirrored finish. Alternatively, a mirror film may be applied to component 1230. In FIG. 13a , an embodiment similar to that shown in FIG. 12 is shown but wherein the light enters light guide 1330 internally through surface 1336, reflects off specular or partially specular reflective surface 1335, before exiting light guide 1330 through surface 1337. In combination with channel 1240, this advantageously allows light guide 1330 to block dust from reaching detector 111. Surface 1336 may be angled at between 80° and 100° relative to touch surface 140.

In FIG. 13b , an embodiment similar to that shown in FIG. 13a is shown in which channel 1240 comprises a light transmissive material having a similar refractive index to component 1331. Alternatively, light guide 1331 and channel 1240 are formed from a continuous light guide component. This advantageously allows light guide 1331 to be easily clamped to the glass, improving tolerances.

In FIG. 14, an embodiment similar to that shown in FIG. 13b is shown where light guide 1330 and channel 1240 are formed from a continuous light guide component 1430. This advantageously prevents any paths for ambient light to reach detector through surface 1435. The light enters light guide 1430 internally through surface 1436, reflects off specular or partially specular reflective surface 1435, before exiting light guide 1430 through surface 1437. Support components 1450 may be used to mount light guide 1430 to an external frame (not shown) and to panel 150. Support components 1450 may comprise a light absorbent material and perform essentially the same optical function as light absorbent surfaces 1250 in earlier embodiments.

In FIG. 15, an embodiment similar to that shown in FIG. 14 is shown where light guide component 1430 has top edge 1545 having a radius. Due to manufacturing limitations, it difficult to ensure a sharp edge. A sharp edge may also be dangerous to a user. Therefore, a radius of the edge is assumed. Although light guide component 1430 may be designed to minimize ambient light from reaching detector 111, the radius of edge 1545 will inevitably allow light from undesirable angles to enter the light guide and consequently reach detector 111. Similarly, an edge 1540 at the bottom of surface 1536 may reflect light at undesirable angles when not perfectly sharp. Consequently, in one embodiment, edge 1540 is positioned below the plane of touch surface 140 and shielded by absorbent material 1450. Preferably, edge 1545 and edge 1540 have a radius of 0.1 mm.

In FIG. 16, an embodiment similar to that shown in FIG. 14 is shown where light guide component 1430 further comprises extended lip 1680.

In FIG. 17, an embodiment similar to that shown in FIG. 14 is shown where light guide component 1730 comprises a channel having at least two channel axes 1761, 1762. In this embodiment, light 120 enters light guide 1730 internally through surface 1736, internally reflects off specular or partially specular reflective surface 1735 as well as surface 1731 and/or surface 1732 before exiting light guide 1730 through surface 1737 to reach detector 111. Light 120 is internally reflected by at least two surfaces before reaching a detector. This advantageously allows the more flexible positioning of emitter/detector components with respect to the panel 150 and the minimisation of the width of components from edge 155.

In FIG. 18, an embodiment similar to that shown in FIG. 15 is shown where emitters 110 and detectors 111 are mounted on substrate 1860. In this embodiment, support components 1550 comprise support slot 1870, which provide physically supports substrate 1860.

In FIG. 19, an embodiment similar to that shown in FIG. 15 is shown where light guide component 1930 comprises a bottom coupling surface 1937 providing a dioptric power. The light 120 enters light guide 1930 internally through surface 1936 and reflects off specular or partially specular reflective surface 1535. The light then exits light guide 1930 through bottom coupling surface 1937 and is converged on to the detectors 111 by the optical power of bottom coupling surface 1937. In the transmitter role, the light emitted by emitters 110 is substantially columnated by the optical power of bottom coupling surface 1937. This advantageously allows the capture of a larger angular distribution of light 120 from emitter 110 and collimating the light to direct it to surface 1535. This feature of the surface coupling light to a detector or from an emitter having a dioptric power may be applied to any of the embodiments provided in the present description comprising a light guide. The curvature angles are preferably within 5-10 mm per radius of curvature.

In FIG. 20, an embodiment similar to that shown in FIG. 15 is shown where light guide component 2030 comprises a top coupling surface 2036 providing a dioptric power. The light 120 enters light guide 2030 internally through top coupling surface 2036 and reflects off specular or partially specular reflective surface 1535. The light 120 is substantially columnated by the optical power of top coupling surface 2036 where the power is convex. The light then exits light guide 2030 through bottom coupling surface 1937 and is converged on to the detectors 111 by the optical power of top coupling surface 2037. In the transmitter role, the light emitted by emitters 110 is substantially columnated by the optical power of top coupling surface 1937 where the power is concave. This advantageously spreads out light beam 120 vertically, reducing tolerance problems for component alignment. Where the power is convex, light beam 120 is made narrower but more intense. This feature of the surface 2036 having a dioptric power may be applied to any of the embodiments provided in the present description comprising a light guide. The curvature angles are preferably within 5-10 mm per radius of curvature.

In FIG. 21, an embodiment is shown with a feature that may be added to any other embodiment of the disclosure. Protective stop 2190 may be an extension of support component 1550 or a separate component fixed to support component 1550. Protective stop 2190 provides a physical stop which extends further from the touch surface along the normal to the plane of the touch surface than any light guide component (e.g. 1530 as shown in FIG. 21). This protective stop ensures that if the touch apparatus 100 is placed against a flat surface, e.g. a wall or floor, top surface 1535 of light guide component 1530 will not be scratched or damaged by the flat surface, as protective stop 2190 will hold the touch apparatus 100 and light guide component 1530 away from the flat surface, leaving a gap. Preferably, protective stop 2190 extends at least 0.1 mm further from the touch surface along the normal to the plane of the touch surface than any light guide component.

In FIG. 22, an embodiment similar to that shown in FIG. 15 is shown with a zoomed view on top coupling surface 2236, reflective surface 2235, reflective surface edge 2239, light guide 2230, and support components 2250. In this embodiment, an additional light absorbing layer 2210 is provided, wherein light absorbing layer 2210 covers reflective surface edge 2239 and optionally partially overlaps reflective surface 2235. This advantageously allows the reduction of ambient light received through edge 2239 and/or reflected at an undesirable angle from within light guide 2230. This feature may be applied to any of the embodiments provided in the present description comprising a light guide with edges that are exposed to ambient light.

In FIG. 23, an embodiment similar to that shown in FIG. 22 is shown, wherein top coupling surface 2336 is angled relative to the touch surface 140. Top coupling surface 2336 may be angled at between 100° and 80° relative to touch surface 140. This feature of the surface coupling light to or from the touch surface 140 having an angle may be applied to any of the embodiments provided in the present description comprising a light guide.

In FIG. 24, an embodiment similar to that shown in FIG. 22 is shown, wherein top coupling surface 2236 is spaced from panel 150 to provide ditch 2410. Ditch 2410 advantageously allows dust, liquids, or other debris from contaminating the portion of surface 2236 exposed to touch surface 140. This feature may be applied to any of the embodiments provided in the present description comprising a light guide. Preferably, ditch 2410 extends between 0.01 mm and 2 mm below touch surface 140.

In FIG. 25, an embodiment similar to that shown in FIG. 22 is shown, wherein reflective surface 2235, reflective surface edge 2239, and/or top coupling surface 2336 are provided with optical layer 2510. Optical layer 2510 has a lower refractive index than light guide 2230 and may comprise fluoro polymer plastics e.g. Teflon and Cytop, dielectric coatings e.g. magnesium fluoride or nanoporous sio₂. Techniques for applying layer 2510 to surface 2235 may include sputter deposition, spray coating, dip coating, physical/chemical vapour deposition. Protective layer 2510 advantageously prevents the frustration of the internal reflection occurring at surface 2235 whilst not affecting the optical properties of transmission at surface 2236. This feature may be applied to any of the embodiments provided in the present description comprising a light guide with surfaces exposed to ambient light.

In FIG. 26, an embodiment similar to that shown in FIG. 25 is shown, wherein protective layer 2510 is further provided with hard layer 2610. Hard layer 2610 preferably covers surfaces most vulnerable to scratching, namely reflective surface 2235 and reflective surface edge 2239. Hard layer 2610 may comprise dielectric coatings, plastic hard coatings, chromium oxide, metal sheeting, etc. Hard layer 2610 advantageously physically protects coating layer 2510. This feature may be applied to any of the embodiments provided in the present description comprising a light guide with surfaces exposed to ambient light and/or environmental or user wear from contact with objects.

In FIG. 27, an embodiment similar to that shown in FIG. 25 is shown, wherein reflective surface 2235, reflective surface edge 2239, and/or top coupling surface 2236 are provided with hard layer 2710. Hard layer 2710 may comprise e.g. the hard coatings of the previous embodiment that are optically clear as well as standard spectacle lens coatings. Hard layer 2710 advantageously allows scratch protection of the exposed light guide surfaces. This feature may be applied to any of the embodiments provided in the present description comprising a light guide with surfaces exposed environmental or user wear from contact with objects.

In FIG. 28, an isometric view of an embodiment similar to that shown in FIG. 15 is shown with a focus on top coupling surface 2836 and light guide 2830, and support components 2250. In this embodiment, top coupling surface 2836 comprises a vertical corrugation 2810. The corrugation may preferably be sinusoidal with a period length of between 0.1 mm-lmm. This advantageously improves the spread of the light from emerging from surface 2836 in the plane of the touch surface, which allows more scanlines at high angles. This feature of the surface coupling light to or from the touch surface 140 having a vertical corrugation may be applied to any of the embodiments provided in the present description comprising a light guide. 

1. A touch sensing apparatus, comprising: a light transmissive panel that defines a touch surface, a plurality of light emitters and detectors arranged along a perimeter of the light transmissive panel, and a plurality of optical components arranged along the perimeter of the light transmissive panel, wherein the light emitters are arranged to emit a respective beam of emitted light and the optical components are configured to direct the emitted light to a path across the light transmissive panel.
 2. The touch sensing apparatus of claim 1, wherein the optical components comprise a light guide arranged to receive light from the light emitters through a first surface and couple out light travelling in the light guide to the touch surface through a second surface.
 3. The touch sensing apparatus of claim 2, wherein the second surface is diffusively transmissive.
 4. The touch sensing apparatus of claim 2, wherein the light guide further comprises a reflective surface configured to internally reflect light travelling in the light guide from the first surface to the diffusive surface.
 5. The touch sensing apparatus of claim 5, wherein the reflective surface is diffusely reflective, partially diffusely reflective, or specularly reflective.
 6. The touch sensing apparatus of claim 2, wherein the reflective surface is coated by at least one of a high refractive index coating and a scratch resistant coating.
 7. The touch sensing apparatus of claim 2, wherein at least one of the first and or second surfaces comprise a dioptric power.
 8. The touch sensing apparatus of claim 2, wherein at least one of the first and or second surfaces comprise a corrugation.
 9. The touch sensing apparatus of claim 2, further comprising a ditch formed between the second surface and the panel.
 10. The touch sensing apparatus of claim 1, further comprising at least one protective stop mounted to touch sensing apparatus proximal to an optical component and extending further from the touch surface along the normal to the plane of the touch surface than any optical component surface.
 11. The touch sensing apparatus of claim 1, wherein the optical components comprise a reflector surface to reflect light from the light emitters to the touch surface, wherein the reflector surface reflects light diffusively, partially diffusively, or specularly.
 12. The touch sensing apparatus of claim 1, wherein an angular filter is arranged between the optical components and touch surface and configured to only allow light travelling within 10 degrees of the plane of touch surface to pass between the touch surface and the optical components.
 13. The touch sensing apparatus of claim 1, further comprising an elongate channel positioned between each light emitter and/or detector and a surface of a corresponding optical component, wherein the elongate channel comprising channel walls, and wherein at least a portion of the channel walls are configured to absorb light.
 14. The touch sensing apparatus of claim 13, wherein the elongate channel is formed from a light guide, an airgap, or other light transmissive medium.
 15. The touch sensing apparatus of claim 13, wherein the elongate channel is not straight and wherein the channel walls comprise internally reflective surfaces. 